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Soluble TRAIL does not impair the anti-osteoclastic activity of osteoprotegerin: Letter to the editor
No full textIt has been extensively documented that osteoprotegerin (OPG), a soluble member of the TNF receptor superfamily, inhibits osteoclastogenesis by binding to receptor activator of NF-kB ligand (RANKL) and preventing interaction with its cognate transmembrane receptor RANK. However, OPG can also interact with, and neutralize, TNF-related apoptosis inducing ligand (TRAIL), whose extracellular domain shares a 30% homology with the extracellular domain of RANKL. Although some inconsistencies on the differential binding affinity of OPG for RANKL versus TRAIL were present in initial studies, it has been recently demonstrated that the affinity of native OPG for native TRAIL is comparable to that for RANKL (45 nM versus 23 nM, respectively) at 37°C, as determined by plasmon surface resonance analysis. Consistently with this biochemical study, OPG has been shown to act in a paracrine and autocrine manner by binding TRAIL and promoting the survival of multiple myeloma, prostate cancer, ameloblastoma cells and synovial fibroblasts. Interestingly, previous data from different groups have shown that recombinant TRAIL promote monocytic differentiation, while inhibits both human and mouse osteoclastogenesis when added to pre-osteoclast cultures induced to differentiate with recombinant M-CSF+RANKL as well as to mature osteoclasts. On the other hand, a couple of studies suggested that recombinant soluble TRAIL might promote osteoclastogenesis, and the proposed molecular mechanism to explain such observation was a competition between TRAIL and RANKL for OPG binding. However, it should be noticed that Vitosky et al. used much higher concentrations of TRAIL (500 ng/ml) than RANKL (30 ng/ml) or OPG (50 ng/ml) and more importantly used mouse bone marrow pre-osteoclasts. In this respect, it has been clearly shown that mouse pre-osteoclasts only express TRAIL-R2, while human peripheral blood-derived pre-osteoclasts express both death receptors TRAIL-R1 and TRAIL-R2 as well as TRAIL-R4.
Therefore, to further elucidate the important issue of the interply between RANKL, TRAIL and OPG in human osteoclastogenesis, we have cultured adherent PBMC with M-CSF+RANKL for 14 days in the absence or presence of recombinant OPG and recombinant TRAIL, used alone or in combination. Importantly, all cytokines were used at the same concentration (50 ng/ml). As expected [10-13], the addition of TRAIL to M-CSF+RANKL significantly (p<0.05) inhibited osteoclast formation (Figure 1A-B). Of note, recombinant OPG completely abrograted (p<0.05) osteoclast formation irrespectively of the presence of recombinant TRAIL in culture. The anti-osteoclastic activity of OPG could not be ascribed to a low affinity of OPG for TRAIL since OPG (50 ng/ml) efficiently inhibited the apoptosis induced by TRAIL (50 ng/ml) in HL-60 leukemic cells.
Our current observations on one hand confirm that TRAIL has anti-osteoclastic activity and on the other hand indicate that it does not affect the potent anti-osteoclastic activity of OPG at least in the simplified model of osteoclastogenesis represented by human PBMC induced to differentiate by M-CSF+RANKL. Taken together with previous studies, these data also suggest that the relative concentrations of TRAIL, RANKL and OPG in the local microenvironment are likely key determinant for the regulation of osteoclastogenesis
TRAIL and osteoprotegerin: a role in endothelial physiopathology?
No full textIncreasing experimental evidence suggests that both tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) and its soluble decoy receptor osteoprotegerin (OPG) are involved in vascular biology. In particular, emerging data indicate that recombinant soluble TRAIL may act as a molecule with potential anti-inflammatory activity in vascular physiopathology. Conversely, the presence of leukocytes expressing membrane-bound TRAIL in atherosclerotic lesions might be involved in the destabilization of atherosclerotic plaques by inducing apoptotic cell death of vascular smooth muscle cells in an inflammatory milieu. Also OPG seems to be involved in vascular homeostasis, by acting in a paracrine or autocrine manner as a survival factor for endothelial cells. However, an increased production of OPG may have a role in the development of vascular dysfunction likely by multiple potential mechanisms, not only related to its ability to neutralize TRAIL-activity but also mediated by its heparin-binding domain. In this review we have summarized and discussed both in vitro and in vivo data that suggest potential roles of TRAIL and OPG in vascular physiopathology. Further studies are needed to address how the TRAIL/OPG interaction, their reciprocal balance and/or interplay affect vascular biology in order to design innovative therapeutic strategies in vascular diseases
Receptor activator of nuclear factor kappa B ligand(RANKL) modulates the expression of genes involved in apoptosis and cell cycle in human osteoclasts.
No full textABSTRACTIt has been clearly established that receptor activator of nuclear factor kappa B ligand (RANKL) is a key cytokine involved in the differentiation of osteoclastic precursors of momocytic/macrophagic lineage. However relatively little information is available on the ability of RANKLE to modulate the expression of genes controlling cell survival/apoptosis and proliferation in human osteoclastic cells in comparison to macrophages. For this purpose, CD14+ human periferal blood mononuclear cells, which express the cognate high affinity receptor activator of nuclear factor kappa B (RANK), were differentiated alog the macrophagic or osteoclastic lineage by adding macrophage- colony stimulating factor (M-CSF) or M-CSF plus RANKL in culture for 12 days. RANKL up-regulated the expression of chemokine MIP1 alpha, which potentiates osteoclasic differentiation and simultaneously activated both antiapoptotic (Bcl-2) and pro-apoptotic (CIDEB, PYCARD, and BAK-1) genes. Moreover, RANKL markedl
Dexamethasone counteracts the anti-osteoclastic, but not the anti-leukemic, activity of TNF-related apoptosis inducing ligand (TRAIL).
No full textWe have analyzed the effect of the synthetic glucocorticoid dexamethasone, used alone or in combination with recombinant TRAIL, on in vitro osteoclastic differentiation of peripheral blood-derived macrophages cultured in the presence of macrophage-colony stimulating factor (M-CSF) + RANKL for 12-14 days. Dexamethasone exhibited different effects based on the concentration used. Indeed, while at 10(-7) M dexamethasone reduced the number of mature osteoclasts, at 10(-8) M showed no significant effects and at 10(-9) M significantly increased the number of mature osteoclasts, with respect to cells cultured with only M-CSF + RANKL. On the other hand, the addition in culture of recombinant TRAIL inhibited the output of mature osteoclasts induced by M-CSF + RANKL. However, the presence of dexamethasone (10(-8) or 10(-9) M) into the culture medium significantly counteracted the anti-osteoclastic activity of TRAIL. In order to ascertain whether dexamethasone, might also interfere with the anti-leukemic activity of TRAIL, the degree of apoptosis induced by TRAIL was evaluated in several myeloid (OCI, MOLM, HL-60) and lymphoid (SKW6.4, MAVER, BJAB) leukemic cell lines. The levels of TRAIL-triggered apoptosis were not significantly different between leukemic cells cultured in the absence or presence of dexamethasone. Concerning the molecular mechanism mediating the dexamethasone-suppression of the TRAIL activity in pre-osteoclasts, but not in leukemic cells, we found that dexamethasone induced a significant down-regulation of the surface levels of TRAIL-R2 in cells of the osteoclastic lineage but not in leukemic cells. The ability of dexamethasone to counteract the TRAIL pathway envisions a novel mechanism mediating the pro-osteoclastic activity of dexamethasone in vivo
Perifosine selectively induces cell cycle block and modulates retinoblastoma and E2F1 protein levels in p53 mutated leukemic cell lines.
No full textThe effect of the single-chain alkylphospholipid perifosine was analyzed in p53(wild-type) (SKW6.4, OCI and MOLM), p53(mutated) (BJAB, MAVER) and p53(null) (HL-60) leukemic cell lines. Perifosine promoted cytotoxicity with a combination of apoptosis induction in all cell lines and cell cycle block at the G(2)M checkpoint, which was selectively observed in p53(mutated) BJAB and MAVER cell lines. At the molecular level, perifosine induced hypophosphorylation of retinoblastoma protein and the degradation of E2F1 protein in p53(mutated) but not in p53(wild-type) cells. These data indicate that perifosine potentially represents an innovative therapeutic approach for p53(mutated) hematological malignancies
Dexamethasone counteracts the anti-osteoclastic, but not the anti-leukemic, activity of TNF-related apoptosis inducing ligand (TRAIL)
No full textWe have analyzed the effect of the synthetic glucocorticoid dexamethasone, used alone or in combination with recombinant TRAIL, on in vitro osteoclastic differentiation of peripheral blood-derived macrophages cultured in the presence of macrophage-colony stimulating factor (M-CSF) + RANKL for 12-14 days. Dexamethasone exhibited different effects based on the concentration used. Indeed, while at 10(-7) M dexamethasone reduced the number of mature osteoclasts, at 10(-8) M showed no significant effects and at 10(-9) M significantly increased the number of mature osteoclasts, with respect to cells cultured with only M-CSF + RANKL. On the other hand, the addition in culture of recombinant TRAIL inhibited the output of mature osteoclasts induced by M-CSF + RANKL. However, the presence of dexamethasone (10(-8) or 10(-9) M) into the culture medium significantly counteracted the anti-osteoclastic activity of TRAIL. In order to ascertain whether dexamethasone, might also interfere with the anti-leukemic activity of TRAIL, the degree of apoptosis induced by TRAIL was evaluated in several myeloid (OCI, MOLM, HL-60) and lymphoid (SKW6.4, MAVER, BJAB) leukemic cell lines. The levels of TRAIL-triggered apoptosis were not significantly different between leukemic cells cultured in the absence or presence of dexamethasone. Concerning the molecular mechanism mediating the dexamethasone-suppression of the TRAIL activity in pre-osteoclasts, but not in leukemic cells, we found that dexamethasone induced a significant down-regulation of the surface levels of TRAIL-R2 in cells of the osteoclastic lineage but not in leukemic cells. The ability of dexamethasone to counteract the TRAIL pathway envisions a novel mechanism mediating the pro-osteoclastic activity of dexamethasone in vivo
Receptor activator of nuclear factor kappa B ligand (RANKL) modulates the expression of genes involved in apoptosis and cell cycle in human osteoclasts
No full textIt has been clearly established that receptor activator of nuclear factor kappa B ligand (RANKL) is a key cytokine involved in the differentiation of osteoclastic precursors of the monocytic/macrophagic lineage. However, relatively little information is available on the ability of RANKL to modulate the expression of genes controlling cell survival/apoptosis and proliferation in human osteoclastic cells in comparison to macrophages. For this purpose, CD14+ human peripheral blood mononuclear cells, which express the cognate high affinity receptor activator of nuclear factor kappa B (RANK), were differentiated along the macrophagic or osteoclastic lineage by adding macrophage-colony stimulating factor (M-CSF) or M-CSF plus RANKL in culture for 12 days. RANKL up-regulated the expression of the chemokine MIP1alpha, which potentiates osteoclastic differentiation and simultaneously activated both anti-apoptotic (Bcl-2) and pro-apoptotic (CIDEB, PYCARD, and BAK-1) genes. Moreover, RANKL markedly up-regulated cylin D2, while it significantly decreased the levels of cyclin A, cyclin-dependent kinase 2, and other cyclin-dependent kinases, in keeping with the notion that end-stage osteoclasts are nondividing cells. Finally, a long-term exposure of RANKL up-regulated the adaptor protein TRAF3 but not TRAF6
Perifosine selectively induces cell cycle block and modulates retinoblastoma and E2F1 protein levels in p53 mutated leukemic cell lines.
No full textThe effect of the single-chain alkylphospholipid perifosine was analyzed in p53(wild-type) (SKW6.4, OCI and MOLM), p53(mutated) (BJAB, MAVER) and p53(null) (HL-60) leukemic cell lines. Perifosine promoted cytotoxicity with a combination
of apoptosis induction in all cell lines and cell cycle block at the G(2)M checkpoint, which was selectively observed in p53(mutated) BJAB and MAVER cell lines. At the molecular level, perifosine induced hypophosphorylation of retinoblastoma protein and the degradation of E2F1 protein in p53(mutated) but not in p53(wild-type) cells. These data indicate that perifosine potentially
represents an innovative therapeutic approach for p53(mutated) hematological malignancies
Serum Soluble Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand Levels in Older Subjects with Dementia and Mild Cognitive Impairment
No full textBackground: The tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been involved in both physiological and pathological conditions, including vascular pathologies and pathologies of the central nervous system. Nonetheless, the knowledge about the role of systemic TRAIL in patients affected by different types of dementia and mild cognitive impairment (MCI) is still limited. Objective: We assessed serum TRAIL levels in a large cohort of older individuals (n = 644) including patients with late-onset Alzheimer's disease (LOAD), vascular dementia (VAD), ‘mixed' dementia (MIX), MCI, and healthy controls. Methods: Circulating TRAIL was measured by ELISA. Results: At univariate analysis, TRAIL levels were higher in VAD, MIX, and MCI patients compared with LOAD patients and controls. Using the multiple linear regression model, we found that TRAIL levels were associated with VAD and MCI, but not MIX, independent of potential confounding factors. Conclusion: The finding of high levels of circulating TRAIL in VAD and MCI seems to suggest that both of these conditions are characterized by a significant vascular damage with respect to LOAD
Tumor necrosis factor-related apoptosis-inducing ligand sequentially activates pro-survival and pro-apoptotic pathways in SK-N-MC neuronal cells.
No full textThe SK-N-MC neuroblastoma cell line, which expresses surface tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) receptors TRAIL-R2 and TRAIL-R4, was used as a model system to examine the effect of TRAIL on key intracellular pathways involved in the control of neuronal cell survival and apoptosis. TRAIL induced distinct short-term (1-60 min) and long-term (3-24 h) effects on the protein kinase B (PKB)/Akt (Akt), extracellular signal-regulated kinase (ERK), cAMP response element-binding protein (CREB), nuclear factor kappa B (NF-kappaB) and caspase pathways. TRAIL rapidly (from 20 min) induced the phosphorylation of Akt and ERK, but not of c-Jun NH2-terminal kinase (JNK). Moreover, TRAIL increased CREB phosphorylation and phospho-CREB DNA binding activity in a phosphatidylinositol 3-kinase (PI 3K)/Akt-dependent manner. At later time points (from 3 to 6 h onwards) TRAIL induced a progressive degradation of inhibitor of kappaB (IkappaB)beta and IkappaBepsilon, but not IkappaBalpha, coupled to the nuclear translocation of NF-kappaB and an increase in its DNA binding activity. In the same time frame, TRAIL started to activate caspase-8 and caspase-3, and to induce apoptosis. Remarkably, caspase-dependent cleavage of NF-kappaB family members as well as of Akt and CREB proteins, but not of ERK, became prominent at 24 h, a time point coincident with the peak of caspase-dependent apoptosis
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